Update flake8 requirement from ~=3.7.9 to >=3.7.9,<3.9.0 (larq#489)

* Update flake8 requirement from ~=3.7.9 to >=3.7.9,<3.9.0

Updates the requirements on [flake8](https://gitlab.com/pycqa/flake8) to permit the latest version.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.7.9...3.8.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

* Make flake8 happy

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Lukas Geiger <lukas.geiger94@gmail.com>

⬆️ 0.9.5 (larq#488)

⬆️ 0.9.4 (larq#475)

⬆️ 0.9.3 (larq#464)

Support unknown input shapes with one padding (larq#461)

* Support unknown input shapes

* Support dynamic input shapes in call

* Make shapes lists to be consistent since they are now tensors

* Check multiple data formats

⬆️ 0.9.1 (larq#459)

⬆️ 0.9 (larq#457)

⬆️ 0.8.4 (larq#400)

⬆️ 0.8.3

⬆️ 0.8.2 (larq#341)